As water content quantification methods for solid material samples, there are known: so-called heating method of heating a solid sample at a temperature slightly higher than a boiling point (100° C.) of water and determining the content of water in the sample based on the amount of weight decrease of the sample; and so-called dry method of storing and drying a solid sample, together with a water adsorbing agent such as molecular sieve, silica gel or calcium chloride, in a desiccator and determining the content of water in the sample based on the amount of weight increase of the absorbing agent (see Non-Patent Document 1). There are also widely known: Karl Fischer method for water content determination of solid and liquid samples; a method for water content determination of gas samples by an infrared spectroscope; and a method for water content determination of liquid samples by electric conductivity measurement.
The Karl Fischer method utilizes quantitative reaction of water in the presence of a lower alcohol such as methanol and an organic base such as pyridine as in the reaction scheme (A) and, upon generation of iodine by electrolysis of an electrolytic solution containing iodine ions as in the reaction scheme (B), detects the consumption of the iodine at a detection electrode by reaction with water. As H2O and I2 react at a 1:1 ratio in the reaction scheme (A), the water content of the sample is quantified based on the quantity of electricity required for the electrolysis in the Karl Fischer method.I2+SO2+2H2O+CH3OH+3C5H5N→3C5H5N.HI+C5H5N.HSO4CH3  (A)2I−→I2+2e−  (B)
In the water content measurement method using the infrared spectroscope, the water content of the sample is quantified by detection of an absorption peak of O—H stretching vibration of water at around 3000 to 4000 cm−1 and an absorption peak of H—O—H deformation vibration of water at 1500 to 1700 cm−1.
As one example of the water content measurement method based on the electric conductivity measurement, there is a method of quantifying the content of water (0.01 to 0.4%) in anhydrous hydrofluoric acid by measuring electric conductivity between platinum electrodes as defined by International Organization for Standardization (ISO) (see Non-Patent Document 2). It has also been reported, as another example, that the content of water in SF6 is analyzed by electric conductivity measurement between electrodes (see Patent Document 1).